Thursday, March 17, 2011

User Datagram Protocol (UDP)

The User Datagram Protocol (UDP) is a connectionless transport-layer protocol (Layer 4) that
belongs to the Internet protocol family. UDP is basically an interface between IP and upper-layer
processes. UDP protocol ports distinguish multiple applications running on a single device from one
another.
Unlike the TCP, UDP adds no reliability, flow-control, or error-recovery functions to IP. Because of
UDP’s simplicity, UDP headers contain fewer bytes and consume less network overhead than TCP.
UDP is useful in situations where the reliability mechanisms of TCP are not necessary, such as in
cases where a higher-layer protocol might provide error and flow control.
UDP is the transport protocol for several well-known application-layer protocols, including Network
File System (NFS), Simple Network Management Protocol (SNMP), Domain Name System (DNS),
and Trivial File Transfer Protocol (TFTP).
The UDP packet format contains four fields, as shown in Figure 30-11. These include source and
destination ports, length, and checksum fields.

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